RNA-Seq Study Reveals AP2-Domain-Containing Signalling Regulators Involved in Initial Imbibition of Seed Germination in Rice

A number of internal signals are required for seed germination. However, the precise signalling responses in the initial imbibition of seed germination are not yet fully understood in rice. In this study, the RNA sequencing (RNA-Seq) approach was conducted in 8 h imbibed seeds to understand the signalling responses in the initial imbibition of rice seed germination. A total of 563 differentially expressed genes (DEGs) with at least 4-fold change were identified in 8 h imbibed seeds compared to dry seeds. MapMan analysis revealed that the majority of signalling response-related DEGs were hormone- and transcription factor-related genes, in which the largest number of DEGs belong to the AP2-domain-containing regulators, and their expressions were significantly induced in the initial imbibition of seed germination in rice. Moreover, at least five AP2-domain-containing transcription factor OsDREBs were identified in the initial imbibition of rice seed germination, and the expressions of 251 DEGs were putatively regulated by OsDREBs through the dehydration-responsive element (DRE) cis-element assay. It suggested that the OsDREBs might play important roles in the regulation of initial seed imbibition in rice. The identified genes provide a valuable resource to study the signalling regulation of seed germination in the future.